1. Field of the Invention
The present invention relates generally to a synchronous movement device applied to dual-shaft system including a first shaft and a second shaft. The synchronous movement device includes a driver disposed on the first shaft and a reactor disposed on the second shaft and a link unit connected between the driver and the reactor. In operation, the driver, the link unit and the reactor serve to transmit force to make the first and second shafts synchronously rotate.
2. Description of the Related Art
There are various electronic apparatuses provided with covers or display screens or viewers, such as mobile phones, notebooks, PDA, digital imagers and electronic books. The covers or display screens or viewers are pivotally mounted on the electronic apparatuses via pivot pins or rotary shafts, whereby the covers or display screens or viewers can be freely rotated and opened/closed under external force.
In order to operate the display module (such as the screen) and/or the apparatus body module of the electronic apparatus in more operation modes and application ranges, a dual-shaft mechanism is provided between the display module and the apparatus body module, whereby the display module and/or the apparatus body module can be operated in different operation modes by different rotational angles.
In the above conventional pivot pin structures or rotary shaft structures, generally multiple gaskets with through holes and recessed/raised locating sections, multiple frictional plates and multiple cooperative springs are assembled on the rotary shaft. Two ends of the rotary shaft are respectively fixed by means of retainer rings or retainer members. The springs serve to store energy and release the energy to achieve the objects of rotating and locating the rotary shaft or pivot pin assembly. Basically, the above structures are relatively complicated and it is hard to assemble the structures. Moreover, after a period of operation, the recessed/raised locating sections of the gaskets or frictional plates are likely to wear. This will affect the locating effect.
There is also a conventional mechanism composed of rollers and drive wires (or transmission belts) for transmitting force to the rotary shaft so as to rotate the rotary shaft. As known by those who are skilled in this field, during the operation process of the wires or the transmission belts, delay of kinetic energy transmission will take place. This is because there is a gap between the wires (or transmission belts) and the rollers and the wires (or transmission belts) will slip or untruly operate. Also, the wires (or transmission belts) are made of elastic material and the fixing structure for assembling the wires (or transmission belts) with the rollers is not ideal. As a result, in force transmission, the load on the wires or the pulling force applied to the wires will increase. In this case, the transmission and shift effect of the wires will be deteriorated and the wires may detach from the rollers. Especially, after a period of use, the force of the wires or transmission belts, which is preset in the assembling process will decrease due to elastic failure. Under such circumstance, the synchronous movement effect of the transmission mechanism will be deteriorated.
In some cases, the wires or transmission belts have serious elastic fatigue and often detach from the rollers during the movement of the slide cover module. Under such circumstance, the rotary shaft device will lose its synchronous displacement effect.
There is another problem existing in the application and manufacturing of the wires or transmission belts. That is, during the assembling process of the wires or transmission belts, the wires or transmission belts need to be tensioned. This will make it more difficult to control the quality of wiring and assembling. Therefore, the ratio of good products can be hardly promoted and the assembling time can be hardly shortened. As a result, the manufacturing cost is increased.
In order to improve the above problems, a conventional dual-shaft synchronous movement device has been developed. Such dual-shaft synchronous movement device employs multiple gears for transmitting force. However, as known by those who are skilled in this field, with the transmission gears, the gap between the shafts of the dual-shaft synchronous movement device can be hardly minified. Therefore, the entire transmission unit or structure will occupy a considerably large space. Especially, when the transmission unit is applied to a notebook or a miniaturized electronic device, the electronic device can hardly meet the requirement for lightweight and slimmed design. This is not what we expect.
Various conventional dual-shaft mechanisms are applied to mobile phones or electronic apparatuses. For example, U.S. Pat. No. 7,512,426 B2 discloses a dual-shaft mechanism including a first shaft and a second shaft. The first and second shafts are formed with threaded protrusion sections assembled with inner threads of a block, whereby the block is movable along the first and second shafts.
It should be noted that U.S. Pat. No. 7,512,426 B2 has two problems to be solved or improved as follows:    1. It is necessary to drill the entirely closed block to form inner threads in adaptation to the threaded protrusion sections of the first and second shafts. Therefore, the manufacturing and assembling processes are relatively complicated. Especially, when applied to a sophisticated electronic apparatus such as a mobile phone or the like, the manufacturing and assembling time is prolonged and the difficulty in manufacturing and assembling the dual-shaft mechanism is increased.    2. The threaded protrusion sections of the first and second shafts are assembled with the inner threads of the block. In order to prevent the block from sliding and avoid delay of power transmission in operation, a higher cooperation precision is required. This makes it more difficult and troublesome to manufacture and assemble the dual-shaft mechanism.
Also, there are some conventional mono-shaft hinge structures applied to a door or furniture system. For example, U.S. Pat. No. 4,200,957 discloses a mono-shaft hinge structure including a left flap and a right flap. A sleeve and a shaft are passed through the left flap. The shaft is formed with a hole in which a pin member is inserted to fit with a roller. The right flap is provided with a socket formed with an inclined slot. After the sleeve and the shaft of the left flap are assembled with the socket of the right flap, the pin member fitted on the roller is relatively movable within the inclined slot.
It should be noted that U.S. Pat. No. 4,200,957 is inapplicable to electronic apparatus due to two technical key points as follows:    1. The structure of U.S. Pat. No. 4,200,957 is specifically designed for application to a door. Therefore, it is inapplicable to a mobile phone or an electronic apparatus to synchronously relatively 180-degree (totally 360-degree) rotate the display screen and the apparatus body.    2. According to the structural characteristic and the connection relationship between the components of U.S. Pat. No. 4,200,957, as a whole, it is impossible to simply and directly modify the structure of U.S. Pat. No. 4,200,957 into a dual-shaft system. This is because even if the socket is replaced with two cylindrical structures for mounting two rotary shafts, the power still cannot be transmitted between the two rotary shafts to achieve the object of synchronous movement of the two rotary shafts.
That is, it is impossible to combine U.S. Pat. No. 7,512,426 B2 with U.S. Pat. No. 4,200,957. The structure of U.S. Pat. No. 4,200,957 is a rough mono-shaft system and hard to modify to be mounted on a sophisticated electronic apparatus. The specification of U.S. Pat. No. 4,200,957 fails to specifically recite or suggest how to modify the mono-shaft system into dual-shaft system for achieving synchronous movement of the two rotary shafts.
The conventional rotary shaft structures and the relevant connection components thereof have some shortcomings in use and structural design that need to be overcome. It is therefore tried by the applicant to provide a dual-shaft synchronous movement device and an assembling method thereof to eliminate the shortcomings existing in the conventional rotary shaft structure so as to widen the application range and facilitate the assembling process of the rotary shaft structure.
The synchronous movement device applied to the dual-shaft system of the present invention has the following advantages:    1. The synchronous movement device of the present invention is mounted between the display module and the apparatus body module. When an operator 0°˜180° rotates the display module, the apparatus body module is synchronously relatively 0°˜180° rotated. Therefore, the total rotational angle of the display module and the apparatus body module is 360°. Accordingly, the operator can more quickly and conveniently operate the electronic apparatus in more operation modes (or application ranges). Also, the synchronous movement effect and operational stability of the synchronous movement device and the cooperative rotary shafts are enhanced.    2. The synchronous movement device or transmission mechanism of the present invention is free from any of the gaskets with through holes and recessed/raised locating sections and the frictional plates as well as the springs employed in the conventional rotary shaft structures. Therefore, the problems existing in the conventional technique that the structures are relatively complicated and it is hard to assemble the structures and the recessed/raised locating sections of the gaskets or frictional plates are likely to wear can be apparently improved.    3. The synchronous movement device of the present invention overcomes the problem of delay of kinetic energy transmission of the conventional wires or transmission belts. The synchronous movement device of the present invention also solves the problem of the conventional transmission mechanism that there is a gap between the wires and the rollers so that the wires will slip or untruly operate. The synchronous movement device of the present invention also solves the problem of the conventional transmission mechanism that the fixing structure for assembling the wires with the rollers is not ideal so that in force transmission, the load on the wires or the pulling force applied to the wires will increase to deteriorate the transmission effect.    4. The synchronous movement device or transmission mechanism of the present invention is free from any gear for transmitting force as in the conventional technique. Therefore, the gap between the shafts can be as minified as possible. Therefore, the space occupied by the entire transmission unit or structure is reduced. Accordingly, when the transmission unit is applied to an electronic device, the electronic device can meet the requirement for lightweight and slimmed design.    5. With respect to U.S. Pat. No. 7,512,426 B2, it is necessary to drill the entirely closed block to form inner threads in adaptation to the threaded protrusion sections of the first and second shafts. The processing process is complicated and the processing time is prolonged. The present invention is applicable to a sophisticated electronic apparatus such as a mobile phone or the like to solve the above problem. Moreover, the present invention solves the problems of sliding of the block and delay of power transmission. Especially, the present invention improves the problem of U.S. Pat. No. 7,512,426 B2 that a higher cooperation precision is required. Therefore, the present invention has simpler structure and is easy to manufacture and assemble.    6. With respect to U.S. Pat. No. 4,200,957, the structure of U.S. Pat. No. 4,200,957 is specifically designed for application to a door or furniture system. U.S. Pat. No. 4,200,957 fails to specifically teach how to modify the mono-shaft system into dual-shaft system for achieving power transmission effect. Moreover, the structure of U.S. Pat. No. 4,200,957 is inapplicable to a sophisticated electronic apparatus such as a mobile or the like to synchronously relatively 180-degree (totally 360-degree) rotate the display screen and the apparatus body. The present invention is redesigned to overcome the above problems.